Peel material acidification method

ABSTRACT

A tomato peel material acidification system (10) including a receiving tank (32), a pump (36), acid injection devices (46, 48), mixing devices (38, 39), and a return line (52) for recirculating tomato peel material with an acid level that is too high. PH sensor probes (56, 58, 60) test the pH level of the tomato peel and acid mixture and appropriate controls direct the opening and closing of valves (50, 51, 54, 55) to re-direct the mixture back into the receiving tank.

TECHNICAL FIELD

The present invention relates to a apparatus and process for adding acidto tomato peel material after removal of the peels from tomatoes for thepurpose of establishing a desirable pH.

BACKGROUND ART

In automated tomato processing facilities, it is common to processtomato peels after removal from tomatoes by adding acid, such as HCLacid, to the tomato peels and then adding the acidified tomato peelmaterial to a product such as pizza sauce, which needs salt. Tomatoestypically have a pH level of about 4.0, but tomato peel material canhave a pH level as high as 13.0 pH when removed by a lye applicatorprocess. It is desirable to lower the pH level, and thus raise the acidlevel of tomato peel material, closer to approximately the 4.0 pH levelof whole tomatoes, so that the peel material is suitable for use inpizza sauces and other commercial food products.

One process for acidifying tomato peels is to introduce batches oftomato peels into an acidification tank, add acid to the peel material,circulate the tomato peels and acid in order to mix the two, and thentest the pH of the peel material. If the pH needs adjusting, theappropriate acid level adjustment is made and the material is mixeduntil the acid level is correct. When the acid level is within anacceptable range, the material is pumped out of the tank and a new batchof tomato peel material is then introduced into the tank to beacidified.

The batch system has several drawbacks, one of which is inconsistentmixing of the tomato peel material and acid, and another of which is aslower than desired processing rate. Full, uniform mixing of the peelmaterial and the acid is not always achieved due to differences in sizeof peel material chunks and due to the limited extent a circulationsystem can fully mix the material. In addition, the batch system isinherently slow because the next batch of tomato peel material cannot beacidified until acid level of the current batch is raised to the desiredlevel. The system and process of the present invention seeks to addressthese problems and provide a continuous system that achieves a quick,uniform acidification rate.

DISCLOSURE OF INVENTION

Briefly described, the acidification system of the present inventioncomprises a pump for circulating tomato peel material through thesystem, an acid injection device for adding acid to the tomato peelmaterial, a mixing device for mixing the tomato peel material and acidafter the acid has been added, and a recirculation line for returningmixed tomato peel material and acid to a point upstream of the acidinjection device.

The provision of a continuous circulation system in combination with arecirculation line, along with a mixing device that thoroughly mixes thetomato peel material with the acid, allows for greatly increased,continuous processing rates over prior art batch systems and alsoprovides improved control over pH levels in the resulting tomato peelmaterial.

According to an aspect of the invention, the mixing device includestubing formed to enhance mixing of the tomato peel material and acid.Preferably, the tubing comprises dimple tubing that is positionedbetween the acid injection device and the recirculation line.

According to another aspect of the invention, the acid injection deviceis adapted to add acid to the tomato peel material at a first acidinjection point and a second acid injection point. In addition, thesystem further comprises a second recirculation line downstream of thesecond acid injection point for selectively returning mixed, acidifiedtomato peel material to a point upstream of the first acid injectionpoint. In this manner, a dual acid injection system is provided, whichincreases the processing rate of the system while enhancing properacidification of the tomato peel material by reducing the amount ofmaterial requiring recirculation.

According to yet another aspect of the invention, the mixing devicecomprises a first mixing device downstream of the first acid injectionpoint and a second mixing device downstream of the second acid injectionpoint. Provision of two mixing devices, each after an acid injectionpoint, increases thorough mixing of the tomato peel material prior to pHtesting.

The present invention also includes a process for adding acid to tomatopeel material comprising the steps of pumping the tomato peel materialfrom a receiving tank; as the tomato peel material is being pumped,adding acid to the tomato peel material; mixing the tomato peel materialand acid; and testing the pH level of the tomato peel material and acidmixture; and alternatively or collectively, if the pH level is too high,then adding more acid to the tomato peel and acid mixture, and/or if thepH level is too low, returning the tomato peel and acid mixture to thereceiving tank.

According to an aspect of the process of the invention, an additionalstep is provided of temporarily storing the tomato peel and acid mixturein an acidification tank prior to adding additional acid to the mixture.An additional acidification tank allows for increased mixing time toensure thorough mixing of the tomato peel material and acid, which maybe desirable and/or necessary for some applications.

These and other features, objects, and advantages of the presentinvention will become apparent from the following description of thebest mode for carrying out the invention, when read in conjunction withthe accompanying drawings, and the claims, which are all incorporatedherein as part of the disclosure of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Throughout the several views, like reference numerals refer to likeparts, wherein:

FIG. 1 is a schematic diagram of a first embodiment of a peel materialacidification system; and

FIG. 2 is a schematic diagram of a second embodiment of a peel materialacidification system.

BEST MODE FOR CARRYING OUT THE INVENTION

Reference will now be made in detail to the preferred embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. While the invention will be described in conjunction with thepreferred embodiments, it will be understood that the describedembodiments are not intended to limit the invention specifically tothose embodiments. On the contrary, the invention is intended to coveralternatives, modifications and equivalents, which may be includedwithin the spirit and scope of the invention as defined by the appendedclaims.

FIG. 1 shows a first embodiment for a peel material acidification system10 that is designed for use in acidifying tomato peel material that isreceived from a tomato peeler system 12. Tomato peeler system 12 isshown for exemplary purposes and the particular type of peeler equipmentused to remove tomato skins from whole tomatoes is not germane to thepresent invention. As designed, the peel material acidification systemof the present invention processes tomato peel material regardless ofthe process used to remove the skins.

Briefly, the illustrated tomato peeler system 12 includes a caustic lyeapplicator 14 where sodium hydroxide (NaOH) solution is applied to thetomatoes to loosen the skins from the bodies of the tomatoes. Thetomatoes are then moved through a scrubber 16 and a pinch roller 18where the skins are scrubbed or pulled from the tomato bodies. Wholepeeled tomatoes 20 are then transferred to processing lines for canning,typically either as whole, diced, crushed or pureed tomatoes. Myco-pending patent application, Ser. No. 09/103,798 now abandonedentitled "Sorter and Method for Sorting Soft and Broken Tomatoes"describes tomato processing operations in more detail.

From the scrubber 16 and pinch roller 18, tomato peel material 22 istransferred to a comminuting machine 24 where the peel material ischopped to a near paste consistency prior to acidification. Finelychopping the peel material has been found to be important to theacidification process because it enhances uniform acidification of thepeel material. From the comminuting machine 24, tomato peel material 26is pumped to a holding tank 28, which may or may not be necessary,depending on the processing facility.

Peel acidification system 10 receives tomato peel material 26 fromholding tank 28 via a pump 30 and holds the material in a receiving tank32, which includes an agitator 34 for stirring the tomato peel material.Receiving tank 32 functions as an inlet station for the acidificationsystem. A second pump 36 pumps the tomato peel material from receivingtank 32 through a flow path generally defined by conduit line 40. Theflow path includes at least one mixing device, which for example maycomprise a first dimple tubing length 38 and a second dimple tubinglength 39. The tomato peel material is pumped through conduit line 40 toan outlet station in the form of a storage holding tank 42 or tosubsequent processing equipment.

System 10 also includes an acid storage tank 44 and a pair of acidinjection pumps 46, 48, which function as acid injection points whereacid is introduced into the tomato peel material. Acid injection pump 46preferably introduces acid at a point between system pump 36 and thefirst set of dimple tubing 38. In this manner, dimple tubing 38immediately mixes the tomato peel material and the acid after the acidis introduced into the tomato peel material.

Peel acidification system 10 also includes a first return line 49 and adiverter valve 50, which together re-direct the tomato peel and acidmixture back into receiving tank 32 if necessary. A stop valve 51 inline 40 works in conjunction with diverter valve 50 to re-direct tomatopeel material into return line 49. A second return line 52, whichincludes a diverter valve 54, operates in a similar fashion to re-directtomato peel and acid mixture downstream of mixing device 39 back intoreceiving tank 32. A second stop valve 55 works in conjunction withsecond diverter valve 54 to re-direct tomato peel material into returnline 52. First return line 49 draws tomato peel material from line 40prior to the second acid injection pump 48, which may be necessary ifthe pH level is relatively high, while second return line 52 drawstomato peel material from a point downstream of second acid injectionpump 48. Two acid injection pumps and two return lines are provided inorder to make the system more efficient, as discussed later.

Peel acidification system 10 further includes at least one andpreferably three pH probes 56, 58, 60. pH probe 56 tests the pH of thetomato peel and acid mixture immediately after the material passesthrough dimple tubing 38. If the acid level is too high (pH level toolow) or way too low (pH level too high), then diverter valve 50 can beopened and stop valve 51 closed to re-direct the tomato peel and acidmixture back into receiving tank 32. Re-directing the tomato peelmaterial with a high acid level (and low pH) into nonacidified tomatopeel material in the receiving tank dilutes the material and lowers itsacid level (raises the pH of the re-cycled peel material).

If the acid level is too low (high pH), then diverter valve 50 is keptclosed and additional acid is introduced by pump 48, to raise the acidlevel (and lower the pH level) to within an acceptable range. A computercontroller (PC) 61 is electrically connected at 63, 65 and 67 to probes56, 58 and 60 and is responsive to signals therefrom to control flowrates for pumps 46, 48, through electrical connections 69 and 71, inorder to properly adjust the acid level of the tomato peel material.

As schematically shown in the drawing, controller (PC) 61 is illustratedfor convenience at three locations, but preferably controller 61 is asingle controller, which may for example comprise a general purposedigital computer with appropriate software, or a dedicated controllerapparatus. Controller (PC) also communicates control signals tosolenoid-actuated flow control valves 50, 51, 54, 55 and 62 throughelectrical connections 73, 75, 77, 79 and 82, respectively.

Dimple tubing 38, 39 collectively form a mixing device for uniformlymixing the acid with the tomato peel material. While dimple tubing isschematically shown in the drawing, it should be noted that other typesof mixing devices can be used which should be apparent to those skilledin the art. Dimple tubing is desirable because it is relativelyinexpensive and it does not significantly impede the continuous flow oftomato peel material through the system because of its smooth contoursthat do not accumulate material.

Dimple tubing 38, 39 includes approximately 1-inch diameter dimples thatprotrude approximately 3/8 of an inch into the tubing and which arestaggered along the length of the tubing. As the tomato peel and acidmixture passes through the tubing, the inwardly protruding dimplescreate sufficient turbulence to thoroughly mix the tomato peel materialwith the acid. Suitable dimple tubing is disclosed in U.S. Pat. No.5,375,654, issued Dec. 27, 1994. Other types of turbulating heatexchange tubes may also be used.

PH probe 58 works in a similar fashion to probe 56 to test the pH levelof the tomato peel material after passing through dimple tubing 39. Ifthe pH level at this point is not within an acceptable range, thendiverter valve 54 is opened and stop valve 55 closed to re-direct thetomato peel material back into the receiving tank 32. If the tomato peeland acid mixture has an acceptable pH level, diverter valve 54 is keptclosed and valve 55 opened to direct the mixture into storage holdingtank 42.

PH probe 60 is a back-up probe that measures the pH of the tomato peelmixture immediately prior to exiting the system. If the pH level is outof range, then diverter valve 54 is opened and exit valve 55 closed tore-direct the mixture back into the receiving tank 32.

Finally, a back pressure valve 62 is provided immediately downstream ofpH probe 56 and before return line 49. Back pressure valve 62 worksthrough controller (PC) 61 in conjunction with centrifugal pump 36 tomaintain a constant flow rate through conduit line 40 by receivingsignals from a pressure transducer (PT) 83 via electrical connection 85.

Peel acidification system 10 has several advantages over the prior artbatch processing system discussed earlier. First, the present system isa continuous pump-through system where tomato peel material iscontinuously drawn from receiving tank 32 and pumped into storage tank42 (or out of the system to further processing). A continuousflow-through system greatly increases processing rates. Second, returnlines 49, 52 allow for adjustment of the pH level, if necessary, byre-directing the tomato peel and acid mixture back through the system,and work in conjunction with the pump and the mixing system to allow forcontinuous flow of the tomato peel material while making appropriateadjustments to the pH level of the tomato peel material. Third, thedimple tubes of the mixing device are made a part of the flow-throughconduit and thus allow for continuous pumping while providing thoroughmixing of the tomato peel material. These advantages, individually andcollectively, provide a significantly improved system and process foracidifying tomato peel material.

FIG. 2 shows a modified embodiment of the system of FIG. 1. Peelacidification system 110 receives tomato peel material from a peelersystem 12 and acidifies the material in a similar manner to system 10,but does so with additional equipment and steps that may be desirable ornecessary for some applications. Peel acidification system 110 includeall of the components of system 10, but also includes an acidificationtank 112 and a second pump 114 in conduit line 40 to pump tomato peelmaterial from acidification tank 112 to the storage tank 42. A bypassline 116 is provided, which in conjunction with valves 118, 120, canbypass acidification tank 112 if desired. By closing stop valve 51 andvalve 120, and opening valve 118, acidification tank 112 is bypassed andsystem 110 operates like system 10 of FIG. 1. Valves 118 and 120 can bemanual valves or solenoid-actuated and can be electrically connected tocontroller (PC) 61 for control of operation.

For some applications, it may be desirable to provide an acidificationtank to ensure uniform acidification of all of the tomato peel material.This may be particularly necessary if the tomato peel material is notfully chopped up prior to entering the system or if extremely highprocessing rates are necessary. After tomato peel material has hadsufficient time to acidify in acidification tank 112, a final acidadjustment is provided by acid injection pump 48 prior to pumping themixture to the storage holding tank 42. While acidification tank 112temporarily slows flow of the tomato peel and acid mixture, the systemis still considered a continuous, flow-through system due to the factthat the mixture is continuously pumped through tank 42 and mixed at thesame time.

The foregoing descriptions of specific embodiments of the presentinvention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteaching. The embodiments were chosen and described in order to bestexplain the principles of the invention and its practical application,to thereby enable others skilled in the art to best utilize theinvention and various embodiments with various modifications as aresuited to the particular use contemplated. It is intended that the scopeof the invention be defined by the Claims appended hereto when read andinterpreted according to accepted legal principles such as the doctrineof equivalents and reversal of parts.

The invention claimed is:
 1. A continuous process for adding acid totomato peel material comprising the steps of:circulating the tomato peelmaterial from a receiving tank to an outlet station in a flow path, asthe tomato peel material is circulating, adding acid to the tomato peelmaterial, mixing the tomato peel material and acid as the tomato peelmaterial is circulated, and testing the pH level of the tomato peelmaterial and acid mixture as they circulate, and prior to the outletstation, if the pH level is too high, then adding more acid to thetomato peel and acid mixture.
 2. The process of claim 1, and furthercomprising the step of:if the pH level is too low, returning the tomatopeel and acid mixture to the receiving tank.
 3. The process of claim 1wherein the mixing step includes moving the tomato peel and acid mixturethrough dimple tubing.
 4. The process of claim 1 and further comprisingthe step of temporarily storing the tomato peel and acid mixture in anacidification tank prior to adding additional acid to the mixture. 5.The process of claim 1 wherein the step of adding acid to the tomatopeel material includes adding acid at a first acid injection point and asecond acid injection point.
 6. The process of claim 5 wherein the stepof recirculating the tomato peel and acid mixture includes returning themixture to the receiving tank after the first acid injection point andreturning the mixture to the receiving tank after the second acidinjection point.
 7. The process of claim 6 wherein the mixing stepincludes mixing the tomato peel and acid mixture downstream of the firstand second acid injection points.
 8. The process of claim 6 and furthercomprising the steps of sensing pH levels of the tomato and acid mixtureafter mixing occurs downstream of the first and second acid injectionpoints.
 9. The process of claim 8 and further comprising the steps ofcontrolling valves in the flow path to direct the tomato peel and acidmixture to the outlet station and to return the tomato peel and acidmixture to the receiving tank.
 10. A continuous process for adding acidto tomato peel material comprising the steps of:circulating the tomatopeel material from a receiving tank to an outlet station in a flow path,as the tomato peel material is circulating, adding acid to the tomatopeel material, mixing the tomato peel material and acid as the tomatopeel material is circulated, and testing the pH level of the tomato peelmaterial and acid mixture as they circulate, and prior to the outletstation, if the pH level is too low, returning the tomato peel and acidmixture to the receiving tank.
 11. The process of claim 10, and furthercomprising the step of:if the pH level is too high, then adding moreacid to the tomato peel and acid mixture.
 12. The process of claim 10wherein the mixing step includes moving the tomato peel and acid mixturethrough dimple tubing.
 13. The process of claim 10 and furthercomprising the step of temporarily storing the tomato peel and acidmixture in an acidification tank prior to adding additional acid to themixture.
 14. The process of claim 10 wherein the step of adding acid tothe tomato peel material includes adding acid at a first acid injectionpoint and a second acid injection point.
 15. The process of claim 10wherein the step of returning the tomato peel and acid mixture includesreturning the mixture to the receiving tank after the first acidinjection point and returning the mixture to the receiving tank afterthe second acid injection point.
 16. The process of claim 15 wherein themixing step includes mixing the tomato peel and acid mixture downstreamof the first and second acid injection points.
 17. The process of claim16 and further comprising the steps of sensing pH levels of the tomatoand acid mixture after mixing occurs downstream of the first and secondacid injection points.
 18. The process of claim 17 and furthercomprising the steps of controlling valves in the flow path to directthe tomato peel and acid mixture to the outlet station and to return thetomato peel and acid mixture to the receiving tank.